High-pressure, coiled-tubing, jet-cleaning technology provided a Mobile Bay operator with a viable option to remove downhole scale and debris efficiently without adversely affecting the formation, the environment, or the well-completion tubulars. This paper will provide a complete and detailed discussion of the surface and downhole equipment needed to perform the high-pressure cleaning application. The paper also provides an overview of the computer simulations created to predict coiled-tubing stresses accurately and the equipment used to collect real-time data on coiled-tubing fatigue, applied pump and hydraulic pressures, tubing drag and buckling parameters, cleaning fluid characteristics, and high-pressure nozzle design. Historically, well-intervention alternatives have been limited in the deep-sour environment of the Mobile Bay field, which lies off the coast of Alabama in the Gulf of Mexico. Such factors as the sour-gas environment, the great depth of the formations (approximately 22,000 ft), the excessive bottomhole temperature (>400 degree), the high wellhead pressure (>5,000 psi), and stringent environmental regulations, present adverse conditions that challenge the use of conventional well-intervention and workover technology. Recently, a Mobile Bay operator experienced barium-scaling problems in a deep well (22,000 ft). A conventional workover risked formation damage as a consequence of killing the well, and damage to the well's expensive exotic alloy completion tubulars during the pulling and reinstallation process. Conventional rig mobilization and day rates were also prohibitive, as were the associated environmental issues inherent in Mobile Bay operations.